The present invention relates generally to a method and apparatus for adjusting characteristics of a device. More particularly, the present invention relates to a method and apparatus for adjusting characteristics of a device used at low temperature in which characteristics of the device can be adjusted at a temperature at which the device is actually used and without causing deterioration of the device.
A process of extracting and adjusting various characteristics of a device used at low temperature is one of very important processes in the fabrication of the device. An example of such device is a high temperature superconductive filter.
In order to extract or measure and to adjust characteristics of the device used at low temperature, there is known a method in which the device is adjusted while cooling the device in vacuum condition by using a freezer. Also, there is known a method in which the device is adjusted while cooling the device directly or indirectly by using cryogen or freezing mixture such as liquid nitrogen, liquid helium and the like. See Japanese utility model laid-open publication No. 4-96849, Japanese patent laid-open publication No. 62-190844, Japanese patent laid-open publication No. 1-163570 and the like.
However, among the methods mentioned above, when the method is used in which a device is adjusted while cooling the device in vacuum condition by using a freezer, it is necessary to introduce a freezer which is expensive. Therefore, manufacturing cost of the device becomes high.
Also, when the freezer is used, the time required for cooling the device to a desired temperature becomes longer than the time required for cooling the device to the desired temperature by using the cryogen. Therefore, the time required for adjusting the device becomes long.
On the other hand, when the method is used in which the device is adjusted while cooling the device directly or indirectly by using cryogen or freezing mixture such as liquid nitrogen, liquid helium and the like, the device is conventionally adjusted while cooling the device by using the cryogen in an atmosphere of air, and it is possible to cool the device enough by the cryogen.
In this method, it is possible, by using inexpensive liquid nitrogen, to rapidly cool and adjust a device, for example, a device which uses high temperature superconductor. Therefore, it is possible to greatly shorten the time required for adjusting the device, and to shorten the time required for manufacturing the device.
However, in the above-mentioned method in which the device is cooled by the cryogen in the atmosphere of air, among gas components contained in the atmosphere of air, gas component or components which become liquid or solid at the temperature to which the device is cooled coagulate and attach to the device. Therefore, there is a possibility that the device is deteriorated.
For example, in the device which uses high temperature superconductor, moisture contained in air in a room temperature coagulates at low temperature, and, especially, the coagulated moisture is liquefied during the temperature fall and temperature rise. Therefore, the liquefied moisture reacts with and invades the superconductor, and thereby the device is deteriorated.
Therefore, it is an object of the present invention to provide a method and apparatus for adjusting a device used at low temperature in which the device is not deteriorated due to the adjustment work of the device.
It is another object of the present invention to provide a method and apparatus for adjusting a device used at low temperature in which gas component or components contained in the atmosphere do not coagulate and attach to the device and the device is not deteriorated thereby.
It is still another object of the present invention to provide a method and apparatus for adjusting a device used at low temperature in which adjustment of the device is performed in the environment that do not include gas component or components coagulating and attaching to the device while cooling the device with cryogen and thereby the device is not deteriorated.
It is still another object of the present invention to obviate the disadvantages of the conventional method and apparatus for adjusting a device used at low temperature.
According to an aspect of the present invention, there is provided a method for adjusting a device used at low temperature comprising: disposing the device used at low temperature within an atmosphere of substitutional gas; cooling the device used at low temperature by using cryogen having a temperature near the temperature at which the device is used; and measuring and adjusting characteristics of the device used at low temperature.
In this case, it is preferable that the temperature of the cryogen is controlled by changing a pressure of the atmosphere of substitutional gas and thereby the temperature of the device is controlled.
It is also preferable that the atmosphere of substitutional gas is an atmosphere confined within a sealable glove box, and the device used at low temperature is placed on a cooling stage disposed within the sealable glove box and partially soaked in the cryogen stored in a bath which is disposed within the sealable glove box, thereby the device used at low temperature is cooled via the cooling stage by the cryogen having a temperature near the temperature at which the device is used.
It is further preferable that the temperature of the device is controlled by using a temperature control portion which is disposed between the cooling stage and the device used at low temperature and which controls a temperature difference between the cooling stage and the device. It is advantageous that the device cooled by the cryogen is heated to a room temperature by using a hot plate.
It is also advantageous that the substitutional gas comprises gas or gases selected from a group consisting of an inert gas, a gas produced by the evaporation of the cryogen and a gas which does not invade the device.
It is further advantageous that vacuum atmosphere is used in place of the atmosphere of substitutional gas.
It is preferable that a material of the device used at low temperature includes a superconductive material.
It is also preferable that the superconductive material is a high temperature superconductive material.
It is further preferable that the device used at low temperature is a device including a band-pass filter having electrodes made of a high temperature superconductive material.
According to another aspect of the present invention, there is provided an apparatus for adjusting a device used at low temperature comprising: a sealable glove box within which the device used at low temperature can be disposed and which can be filled with substitutional gas; and a bath disposed within the sealable glove box and storing cryogen, the cryogen being used for cooling the device used at low temperature and having a temperature near the temperature at which the device is used; wherein characteristics of the device used at low temperature are measured and adjusted while cooling the device by using the cryogen and in the atmosphere of substitutional gas.
In this case, it is preferable that the temperature of the cryogen is controlled by changing a pressure of the atmosphere of substitutional gas and thereby the temperature of the device is controlled.
It is also preferable that the apparatus for adjusting a device used at low temperature further comprises a cooling stage which is partially soaked in the cryogen stored in the bath, wherein the device used at low temperature is placed on the cooling stage, thereby the device used at low temperature is cooled by the cryogen having a temperature near the temperature at which the device is used.
It is further preferable that the apparatus for adjusting a device used at low temperature further comprises a temperature control portion disposed between the cooling stage and the device used at low temperature and the temperature of the device is controlled by controlling a temperature difference between the cooling stage and the device used at low temperature thereby.
It is advantageous that the apparatus for adjusting a device used at low temperature further comprises a hot plate which is disposed in the sealable glove box and by which the device cooled by the cryogen is heated to a room temperature.
It is also advantageous that the substitutional gas comprises gas or gases selected from a group consisting of an inert gas, a gas produced by the evaporation of the cryogen and a gas which does not invade the device.
It is further advantageous that, in place of the substitutional gas, the device is measured and adjusted in vacuum atmosphere.
It is preferable that materials constituting the device used at low temperature include a superconductive material.
It is also preferable that the superconductive material is a high temperature superconductive material.
It is further preferable that the device used at low temperature is a device including a band-pass filter.